Credit: RUI VIEIRA/AFP/GettyImages

Duchess Kate is up for anything!

Kate Middleton has agreed to join British actress Lisa Maxwell -- who is ambassador for the charity Centrepoint -- for Sleep Out, a campaign aimed at raising awareness about London's growing homelessness problem, and will spend a night camped out on the streets of the capital.

Maxwell, 48, told the Daily Mirror that she was introduced to the Duchess of Cambridge, 30, via Prince William, already a Centrepoint patron.

"She asked me about sleeping out, so I said: 'Next time I do it, you're doing it with me. No excuses, [William has] done it.'" Maxwell recounted. "She said: 'You're on'."

Maxwell praised the future Queen as "very savvy and very smart."

William, 30, roughed it on London's streets in December 2009 -- spending time with homeless persons near Blackfriars Bridge.

"He was determined to do it as [Centrepoint] patron to raise awareness of the problem and to be able to understand a little better what rough sleepers go through," Centrepoint's chief executive Seyi Obakin said.